Method of treating vegetable protein

ABSTRACT

The preparation of a bland flavored, vegetable protein food product, preferably a soy protein food product, having excellent and controlled water dispersibility, by forming a slurry of the protein in water, preferably after separating the carbohydrates, sugars, and other nonproteins from the material, heating the slurried material practically instantaneously to elevated temperatures and severely physically working it, preferably by ejecting the slurry material from a nozzle while injecting steam into it, retaining the slurried material at elevated temperatures and under an elevated positive pressure for a brief, controlled time interval, and then suddenly releasing the pressure, volatilizing some moisture along with entrained, objectionable flavor and odor substances, and thereby causing partial cooling, removing the volatilized products and leaving a slurry of sterilized, bland flavored, highly water dispersible protein material, and then preferably drying the slurry to a bland tasting powder which is highly redispersible.

United States Patent Hawley et al.

[54] METHOD OF TREATINGYVEGETABLE PROTEIN [72] Inventors: Robertllawley, Webster Groves; Christopher W. Frederiksen, St. Louis; Ralph A.lloer, Ballivin, all of Mo.

[73] Assignee: Ralston Purina Company, St. Louis, Mo. [22] Filed: Mar.27, 1967 [21 Appl. No.: 625,980

Q H P BHQQIQ John V. Ziemba, Let Soy Protein Work Wonders For You. FoodEngineering, May 1966, Vol. 38, No. 5, pp. 82-84, 87-90, 93.

[4 Feb. 15,1972

Primary Examiner-A. Louis Monacell Assistant Examiner-William A. SimonsAttorney-Price, l-lerleveld, l-luizenga & Cooper [57] ABSTRACT Thepreparation of a bland flavored, vegetable protein food product,preferably a soy protein food product, having excellent and controlledwater dispersibility, by forming a slurry of the protein in water,preferably after separating the carbohydrates, sugars, and othernonproteins from the material, heating the slurried material'practically instantaneously to elevated temperatures and severelyphysically working it, preferably by ejecting the slurry material from anozzle while injecting steam into it, retaining the slurried material atelevated temperatures and under an elevated positive pressure for abrief, controlled time interval, and then suddenly releasing thepressure, volatilizing some moisture along with entrained, objectionableflavor and odor substances, and thereby causing partial cooling,removing the volatilized products and leaving a ,slurry of sterilized,bland flavored, highly water dispersible protein material, and thenpreferably drying the slurry to a bland tasting powder which is highlyredispersible.

14 Claims, No Drawings This invention relates to food, the thepreparation of vegetable protein food products of controlled, highdispersibility, and more particularly to a method of preparing acompletely bland flavored, vegetable protein food and a bland flavoredsoy protein food of high dispersibility, and food products madetherefrom.

This invention was conceived and developed largely for soy materialsbecause of the special problems encountered with such materials.Therefore, it will be explained largely with respect to soy materials,and has special application to such materials, although it can be usedfor other vegetable protein materials in the broader aspects of theinvention.

The preparation of vegetable protein products by a variety of processesis known, including that of soy protein products, usually from isolatedsoy protein obtained from oil extracted soy meal. If such products fromsoy materials are prepared for human or animal consumption, they arenormally designated edible soy protein. The product is high in proteincontent and has a substantial food potential.

However, as is known to those skilled in the processing of soy material,and to purchasers and potential purchasers, this product retains adefinite undesirable odor and flavor characteristic of all soy products.The flavor characteristic is commonly referred to as bitter or beany.Just what causes this flavor is not known, but itis believed to be dueto trace materials tenaciously retained by or in themolecular proteinstructure. These proteins, of varying types, have complex molecularstructures of twisted or helical configuration, and are sometimesreferred to as protein bundles. Tremendous efforts havebeen exerted bymany persons in the past few decades in efforts to eliminate thisextremely troublesome flavor and odor problem, because it presents asubstantial block to widespread adoption of the product as a food.Several techniques suggested do improve the product by reducing theseundesirable characteristics somewhat. These techniques include theaddition of special reagents such as acetic, hydrochloric,sulfuric,-phosphoric, and sulfurous acids, dilute ammonia, carbondioxide, ethylene, steam diluted with carbon dioxide and nitrogen, andothers. They include extraction of oil from the soybean meal flakes withethanol, treatment with certain enzymes, batch autoclaving or. openkettle boiling of the materials for long periods of time, with orwithout agitation. Such treatments are derived using empirical: methodsbecause very little is really known about the structural makeup, andespecially the behavior of such materials upon being subjected tovarious treatments.'Such heating treatments involve substantialdifficulties because of the fact that when the material is heated aboveabout 160 F gelatin occurs which seriously limits the usefulness of theproduct, because the product is extremely tough and rubbery, so as to behardly edible, and is largely insoluble in water. This resulting productcan only be changed by heating it for several hours to actuallybreakdown the molecular structure. This is undesirable from a processingviewpoint, and because of resulting limitations of the productusefulness. In fact, heating of these vegetable proteins as byautoclaving, particularly soy proteins, normally results in almostinedible products.

Even when these relatively complex and costly techniques are employed,some of the bitter or beany flavor and odor characteristics remain, eventhough developers of such techniques have proclaimed their products as"bland." This retention of part of the undesirable flavor has in factprevented the currently produced products from being acceptable bypurchasers except where the flavor can be heavily Further, heattreatment of these vegetable proteins normally drastically reduces thefunctional properties thereof. More specifically, although the aqueousdispersibility (capacity to partially form a colloidal suspension and topartially dissolve in an aqueous fluid) of nonheat treated vegetableproteins is usually relatively high, e.g., about 87 percent, plus orminus, after heat treatment the dispersibility of such materialsfrequently drops to a low dispersibility of about 20 percent or so.Hence, the material will not nicely suspend and dissolve in water toform a milk-type product for example. To be functional the productshould have a high dispersibility of at least more than 50 percent andusually more than 75 percent. Yet the higher the dispersibility, themore pronounced is the undesirable flavor, since flavor cannot bedetected well when dispersibility is low. Therefore, the potentialprocessor has the dilemma of trying to improve functionality bymaintaining high dispersibility while trying to lessen the bitter flavorand odor characteristics which become more noticeable with increase indispersibility.

SUMMARY OF THE INVENTION The major object of this invention is toprovide a method of processing vegetable protein and particularlysoybean protein materials to form 'a completely bland, highly desirable,edible protein product that is free of the so called bitter or beanyflavor and odor characteristics, to such an extent that the product caneven be freely substituted for completely bland products such as milk,andthat has high dispersibility to be functional. Another object is toobtain such aproduct which is also highly functional due to acontrolledhigh dispersibility, that enables excellent grade aqueous suspensions tobe formed. Hence, a resulting milk product is smooth, not chalky orlumpy or granular, as well as pleasant tasting. Yet the novel methodneither requires or employs any special additives or expensive lengthyprocessing and can be practiced without necessarily resulting in a gelproduct. The method can even be practiced in a fashion to give avegetable protein product of no gelation, as is normally desired, or oneof a controlled degree of gelation, as desired. The resulting productneeds no flavor masking, but rather can be used directly as a food, andalso will blend smoothly with products containing other flavoringswithout altering the character of the other flavorings.

Moreover, the novel soy treating process can be operated on anautomated'continuous flow basis, with a minimum of operating personnel,and with a high production output rate.

The basic unique product obtained is one of excellent tastecharacteristics and excellent functionality. It is highly dispersiblefrom a'dry state. Yet, it is'treated with a process involving heat andelevated temperatures. The product uniquely has an optimum combinationof properties not obtainable heretofore, in having a highdispersibility, e.g., of about 86 percent or. so as desired, withresulting high functionality, and also having the excellent flavor freeof the characteristic soy flavor. Hence, it can be used as a foodproduct in various forms, with high protein content. It also can beselectively added to a wide variety of other food products to effectspecial results, adding controlled protein content without objectionableflavor results.

The novel process preferably treats the soy material as an aqueousslurry with controlled, rapid, dynamic heating to an elevatedtemperature range and with momentary physical masked by otherflavorings, or can be placed in products of those unable to complain,such as babies. Present soy protein products certainly cannot besubstituted for completely bland products such as milk, for example,without being subject to instant detection. This limitation is verysignificant and very real.

working under dynamic conditions and under controlled positive pressureand elevated temperature conditions to expose and loosen the tenacioushold of the obnoxious substances by the complex protein molecules. Theso-treated slurry is retained for a brief controlled retention period atelevated temperature and under positive pressure. Then the releasedobnoxious substances are removed by causing subsequent instant pressurerelease to cause flash off, with vaporizing of some moisture that isladen with the entrained odiferous obnoxious substances, followed byseparation of the vaporized materials from the slurry. The slurry isthen dried to an attractive redispersible white powder. The product doesnot form a gel unless the range of solids, treating temperatures, andholding times are regulated to form a product of controlled degree ofgelatin. The full nature and significance of the process and productwill be understood upon studying the detailed description to follow.

As is well known, the interrelated chemical and physical characteristicsof natural food substances are so extremely complex that very little istruly known or understood about them. Research into the behavior andnature of these characteristics and the changes caused in them underdiffering conditions and treatments is dependent almost entirely upon anempirical approach. Further, the acceptance of such materials by humansor animals, and the degree of usefulness of such by the human system orby animal systems is also predominantly experimental. This is true ofnaturally occurring vegetable protein materials such as soybeans,peanuts, linseeds, cotton seeds, sesame seeds, and sun flower seeds, themost significant ones. Extensive research has been conducted on these inefforts to develop useful food products. As a result, some of thesematerials are presently being processed on a relatively limited basis toproduce food products commonly called edible vegetable proteins.

Even though such vegetable protein materials can be processed in amanner to render them useful as food, however, a very significantlimitation on actual acceptance of such exists because of theundesirable flavor, odor and appearance of such. This is a particularlyacute problem with respect to edible protein products prepared fromsoybeans and the bitter, beany flavor and odor, and yellowish appearanceof edible soy protein. As mentioned above, a large number of treatmentshave been suggested for reducing such undesirable characteristics,including the addition of many reactive agents, a variety of cookingprocedures, and the addition of flavormasking reagents. Because a few ofthese suggestions result in a somewhat palatable food product, edibleproteins are presently being prepared and sold for a limited number ofapplications where the residual undesirable flavor and odor will not benoticed or can be masked.

Yet, as is well known, efforts to directly substitute edible proteinsuch as soy protein for completely bland products such as dairyproducts, particularly dried skim milk, have not been successful becausethe undesirable flavor and odor become apparent immediately. Thecharacteristic bitter flavor is readily detected from the yellowishproduct, whether in dry or liquid form. Also, when heated, the productexhibits the characteristic odor. Hence, edible vegetable proteins,particularly those from soybeans, are definitely limited in utility forfood products, as they are presently produced.

The inventor herein, being familiar with the currently produced ediblesoy protein of the assignee herein and with the palatability probleminvolved, decided out of curiosity to try on soy slurry a specialprocess he was working with on another project, to see what wouldhappen. To his surprise and that of other of the assignees employees whohad worked on the flavor and palatability problem, a very practical andinexpensive method of actually removing the residual flavor and odor wasdiscovered using heat and pressure, yet while retaining highdispersibility and functionality. Further experimentation showed thatthe method was totally reliable for these purposes, and further,improved the appearance substantially to cause the product to changefrom yellowish to a more desirable whitish color very similar to skimmilk. The product was not chalky, grainy, or gummy. In fact, the novelproduct even passed the very critical test of being substitutable fordried skim milk without detection. The dried product has excellentredispersibility in water. The flavor is completely bland, enabling theproduct to be employed directly as a food, or in a vast variety of foodsin place of dairy derivative products. The novel product has excellentfood value as well as good palatability. It can moreover be converted tofood products of a variety of shapes and forms, with a controlled degreeof dispersibility, with a controlled degree of gelatin, in liquid orsolid form, with desired flavor additives.

The novel process requires no special chemical additives, or longperiods of treatments. It does not destroy the character of or breakdownthe soy protein. It uses elevated temperatures far above the low rangetemperatures at which the product heretofore would convert to a gel, yetwithout converting to a gel unless this is desired. Also, even thoughheated to high temperatures, no extended cooking is needed tosubsequently breakdown a resulting gel by chemical decomposition of thestructure, as was previously necessary.

This discovery is considered a major breakthrough in the ediblevegetable protein field, particularly for soy protein materials,enabling such materials to now be widely adopted in the food industry toprovide a completely palatable and readily acceptable food frommaterials that could only be used heretofore on a limited basis.Extensive experimentation with food products has proven its completeacceptability, even in products of a bland nature, products requiringheating, and many others.

The unique processing steps are preferably used after certainpreliminary steps are conducted on soybean materials. Because theseunique processing steps are preferably employed in combination withcertain preliminary steps, and because it is desired to explain. theentire process in detail, the invention will be explained herein bydescribing the operation from the beginning.

DESCRIPTION OF PREFERRED EMBODIMENTS This operation will be describedwith respect to soybean and edible soy protein products because this wasthe major area of concern for which the process was discovered, andbecause the process is particularly suited for removing the veryobjectionable flavor and odor of soybean materials.

In brief outline of the total process, the soybeans forming the startingmaterial are ground or crushed, the oil is extracted to leave soybeanmeal or flakes, the proteins and sugars are dissolved out of the flakesinto solution, the proteins are precipitated out of the solution,washed, and put into water suspension as a slurry. The slurry is given acontrolled pH range as discussed in detail hereinafter. The slurry alsohas a controlled range of solids content. It is then instantlydynamically heated to a controlled elevated temperature range, andsubjected to dynamic physical working, preferably of a shearing type,then held at controlled elevated temperatures under positive pressure toprevent vaporization for a brief, controlled time interval. Then thepressure is suddenly released to instantly volatilize part of themoisture and cause objectionable components of unknown type to beentrained by the volatilized moisture, both of which are removed fromthe slurry, resulting in the removal of undesired flavor and odorcharacteristics with retention of high dispersibility well above 75percent, even percent or so. The slurry is then preferably but notnecessarily dried to a white bland flavored powder which has highredispersibility.

More specifically, the soybeans are crushed or ground in convenientfashion, and passed through a conventional oil expeller. The oil ispreferably removed by solvent extraction, using solvents normallyemployed for this purpose.

The resulting solids, commonly referred to as soybean meal, and normallyin the form of flakes, contain many ingredients including complexproteins, sugars, fibers, and others. The proteins and sugars are thenpreferably dissolved out of the solids. This may be done by adding theflakes to an aqueous bath and adding a food grade alkaline material torise the pH substantially above 7. Typical of such alkaline reagents issodium hydroxide, potassium hydroxide, calcium hydroxide or othercommonly accepted food grade alkaline reagents. The material is thencooked for a period of time sufficient to put the proteins and sugars insolution, usually about 30 minutes or so. The resulting liquor solutionis separated from the solids, as by passing the material through ascreen and/or centrifuging. Preferably, the liquor is then cycledthrough a clarifier to remove tiny particles.

The soy proteins are then precipitated from the liquor by lowering thepH to an acidic value of the isoelectric point of the protein, usuallyph of 4.6-4.9, with the addition of a common food grade acidic reagentsuch as acetic acid, phosphoric acid, citric acid, tartaric acid, orothers. The precipitate is then separated as by centrifuging, and washedwith water to remove remaining sugars, except for a minute trace whichis practically impossible to remove. The precipitate is then made intoan aqueous slurry by adding water. The slurry as pretreated forms themost desirable product with respect to the characteristics presentlysought.

This slurry can then be further processed as described in detailhereinafter. However, it is significant to note that this slurry ofisolated soy protein can alternatively be dried, and then subsequentlyrehydrated and further processed in the same manner, as describedhereinafter. Drying of the isolated soy protein is preferably by a flashdry technique such as spray drying or the equivalent, due to retentionof redispersion capacity. The dried material may be stored for a periodof time or immediately reslurried for further processing. It has beenfound that the dried-reslurried material results in a slightly differentfinal product than the final product resulting when the isolated proteinslurry is directly processed further. The technical explanation of thisis not fully understood. The final product from the dried-reslurriedisolated soy protein is slightly inferior for uses such as simulateddairy milk and the like.

The slurry then has its pH adjusted. This is important in order toobtain a final product with high water dispersibility. Specifically, thepH is adjusted to a range of about 5.7 to 7.5, preferably between about6.5 and 7.1. Below about 5.7, the water dispersibility of the finalproduct is very low and not useful for many purposes. However, such aproduct, when specially heated as described hereinafter, can bedesirably used where low dispersibility and bitter-less flavor isuseful, as for example, in baked goods, in cereals, and others. At a pHabove about 7.5 and approaching 8.0, the final product tends to assumean undesirable soapy taste. The degree of dispersibility in the finalproduct can be regulated by varying the pH within the controlled pHrange of about 5.7-7.5, to suit the product to the final food beingprepared. The pH may be easily adjusted by adding a food grade alkalinereagent such as sodium bicarbonate, or even by washing with water for aperiod of time.

The slurry to be further processed should have a controlled solidscontent of about 3-30 percent by weight, and preferably about 5-1 7percent by weight. It if falls below about 3 percent, subsequentprocessing steps are not economically advisable when a continuousprocess is employed. Drying is particularly costly. Above about 17percent solids content, the resulting product does not subsequently lenditself to the preferred flash drying techniques, such as spray dryingusing a jet or spinning thrower or such as a hammer mill type unit, sothat other drying techniques must be employed, to result in a productthat is not as desirable in its functional characteristics. Above about30 percent solids content, brownish discoloration of the product tendsto occur during the processing, probably due to carmelization of theminute amounts of sugars remaining in the slurry.

Each tiny portion of this slurry is then subjected to dynamicinstantaneous heating to an elevated temperature range while also beingdynamically physically worked, preferably almost simultaneously.Currently, the most satisfactory way of achieving this is to pass theslurry through a device commonly known as a Jet Cooker. It includesadjacent jet nozzle orifices, normally concentric, through which theslurry and the pressurized steam used as a heating agent are ejected athigh velocities in intersecting flow patterns, so that each tiny bit ofslurry is instantly dynamically heated by the steam while practicallysimultaneously being subjected to severe physical forces at thenozzleQsuch physical working being largely of a shearing nature. Thephysical working of each tiny portion is believed to expose theobnoxious substances to further action,

and this physical working with the elevated temperature heat treatmentis believed to weaken and/or break the tenacious bond between theseobvious substances and the complex protein molecules, to an extent wherethese substances can be laded away by flashed ofi vapors, as describedhereinafter. This physical working and heating also tends to eliminatesome of the characteristic soy flavor, but more importantly, preparesthe material for the subsequent processing steps. The temperature rangeto which the slurry is heated for the desired results is about 220-400 Falthough the temperature should not be in the lower region of this rangeunless the product is subsequently vented into a vacuum chamber afterbeing held under pressure in a special holding chamber, as explainedhereinafter. Normally the temperature should be about 285-320 F. forbest results. If higher temperatures than about 320 F. are used, theultimate product will tend to develop a gelling nature, with the degreeof gelation being generally in proportion to the increase in temperatureabove this range. Temperatures above about 400 F. are normally notadvisable because of process problems created and lower quality ofresulting product. Temperatures between about 220 F. and 285 F. resultin not quite all the objectionable flavor being removed, although highdispersibility is retained.

The product is introduced to the jet cooker nozzle at a positivepressure. This pressure should be at a value near the pressure of thesteam injected into the slurry, should be sufficient to causehigh-velocity discharge of the slurry through the jet nozzle, and mustbe greater than the pressure in the special retention chamberimmediately downstream of the nozzle. Normally the steam pressure isabout -85 p.s.i.g., the slurry line pressure is slightly above the steampressure, usually about -100 p.s.i.g., and the discharge pressure in thechamber downstream of the nozzle is about 75-80 p.s.i.g. The pressuredrop of the slurry across the nozzle is about 5-l5 p.s.i., dependingupon these other pressures, with 6-10 p.s.i. being common.

The time interval of the slurry in the nozzle is estimated to be about Isecond or less. The nozzle orifice for the slurry is small, being only afraction of an inch, e.g., about one-eighth inch, so that the slurrysolids are subjected to severe dynamic, physical working during passage.The steam intermixes intimately with the solids in the ejected slurry.The amount of steam required is not great, normally being an amount tolower the solids content of the slurry about 1-2 percent by weight.

Preferably the nozzle orifices are concentric, with the slurry beingejected from the center orifice, for example, and the steam from asurrounding annular orifice oriented to cause its output flow path tointersect the output flow path of the center orifice. The slurry andsteam could be ejected from the alternate orifices however. Further, theadjacent orifices need not necessarily be concentric to obtain thisinteraction.

As noted previously, the steam and slurry are ejected into a specialretention chamber. This may comprise an elongated tube through which theintermixed slurry and steam moves from the jet nozzle on one end of thetube to a pressure controlled discharge on the other end. The dischargecan be controlled by a conventional preset pressure release valve toenable continuous process flow from the nozzle to and out of thedischarge valve. This valve regulates the pressure in the holdingchamber. This chamber pressure must be great enough to prevent anysignificant vaporization of the moisture in the chamber, even though thetemperature is well above the boiling point of water. A pressure ofabout 75-80 p.s.i.g. readily achieves this. Since slurry and steam mustcontinuously flow into this pressurized chamber, the pressure behind theslurry and the steam must be greater than the chamber pressure to causethis continuous flow.

The heated slurry is retained in the holding chamber for a definite butrelatively short time period of a few seconds up to a few minutes,normally of about 7 seconds to about seconds. It is only necessary toretain the product in this heated condition for a few seconds foroptimum product. The

time is not too critical in this range, although the longer the slurryis held, the greater the likelihood of gelation of the product withsubsequent release of pressure, particularly at higher temperatures oftreatment. If a degree of gelation is desired, this is an effectivemanner of achieving it. In fact, by increasing the holding time, and/orincreasing the slurry temperature, and/or increasing the percentage ofsolids in the slurry, the operator can controllably increase thegelation of the final product a desired amount.

The pressure on the slurry is then instantly released by discharging theslurry to a reduced pressure zone, into a suitable receiving means. Thiscauses flash off of a portion of the moisture in the form of water vaporwhich is laden with the entrained odiferous, obnoxious pungent chemicalcomponents or substances of unknown composition from the soy product.The flash off also causes substantial cooling of the remaining slurrybecause of the heat of vaporization absorbed from the slurry, so thatthe total time which the product is subjected to elevated temperaturesis very short and controlled. Removal of the substance-laden vaporsremoves the objectionable flavor and odor characteristic. This specialtreatment of the vegetable protein causes retention of the highdispersibility of the raw product in the final product. It usuallydecreases only 1 or 2 percent, e.g., from about 87 percent to about 8586percent for soy protein materials. This is in sharp contrast to adecrease from about 87 percent to about percent or less when heattreated according to conventional teachings. Further, the product iscompletely sterilized by this treatment. Since prior processing involveddefinite difficulties at elevated temperatures, sterilization never wascompletely satisfactory prior to this invention. However, because of thesubstantially elevated temperatures here involved, and the intimatemixture of the hot steam with the slurry, sterilization is greatlyimproved.

The reduced pressure zone into which the slurry is discharged isnormally at atmospheric pressure, but it is sometimes subatmospheric,i.e., at a partial vacuum. In either case, the vapors should beinstantly conducted away from the slurry, preferably by a moving currentof air across the slurry or by drawing a continuous vacuum on thedischarge zone to draw the vapors away. The vapors may be speciallycondensed in a fashion to positively remove the condensate from the areaof the collected discharged slurry. In production, the slurry may bedischarged from the back pressure control discharge valve directly intoa vessel in the open atmosphere where the vapors are allowed and/orcaused to rise directly away from the slurry and are prevented fromcondensing in a manner to allow the condensed substance to flow backinto the product.

To assure complete removal of the vapors from the purified slurrywithout allowing the vapors to recondense back into the slurry, theslurry and vapor should be separated immediately after discharge, i.e.,immediately after pressure release. In this regard it is undesirable tocause passage of both components through a common conduit downstream ofthe discharge valve, and if such is done, it should be minimal.

As noted, the most preferred method of physically exposing and thermallyand physically releasing the objectionable substances from the proteinmolecular bundles, for subsequent carry off, is by use of the jetcooker. it is conceivable that the intimate violent physical treatmentto break up the protein bundles and expose these substances can bepracticed by the use of other equipment such for example by the shearingaction of high pressure pumps, followed by momentary heating in anelevated pressure zone, prior to pressure release and flash off.Moreover, the heating action of the subdivided protein bundles, or theheating plus physical working can conceivably be achieved with alternateequipment such as a hot zone flow tube or coil. Such a device causesrapid flow through a constricted tube, one zone of which is exposed to aheat source such as a gas flame. Other alternative apparatus includesapparatus operating on magento striction principles, apparatus employingradiofrequency heating and agitation, electrostatic heating apparatus,supersonic wave devices, film diaphragm vibration equipment, andreso-jet resonating flame apparatus. In fact, one or more of thesedevices could be combined with the jet cooker to increase the physicalworking action.

The resulting slurried product can then be used directly for foodproducts. It is an attractive white product. If the pH, prior totreatment, was within the stated range, the slurry contains most of thematerial in a partially dissolved state and a partially dispersedcolloidal state that does not tend to settle out. Alternatively, it canbe dried, with the dried product having excellent redispersibility in anaqueous medium.

If the slurry is then dried, preferably the product is flash driedbecause of the uniform, fine, powderous product obtained, the economicalcontinuous processing afforded thereby, and the excellent redispersioncharacteristics of the powder. Of the flash drying techniques, spraydrying is usually used. The product may be freeze dried, but this ismore costly. However, if the solids content of slurry is above about16-17 percent, flash drying becomes difficult or impossible. Then, otherdrying techniques such as drum drying, tray drying, or the like must beemployed, but the dried product tends to be somewhat lumpy.

The dried powder is completely bland to the taste. The bitter flavorcharacteristic of soy protein is gone. It is capable of rapid simplerehydration to a suspension simply by adding water and stirring, becauseof its high redispersion capacity. The product may be used as asubstitute for dairy product derivatives, even dried skim milk, for avariety of purposes. It possesses no strong characteristic soy odor ortaste, even when heated, and in spite of its high dispersibility whichmakes flavor so detectable.

The novel processing not only drastically improves the flavor and odor,provides functionality, and causes quality sterilization, but alsocauses a distinct and advantageous change in appearance. That is, priorto the processing the color is yellowish, particularly as suspended inslurry form. After processing, the product is whitish. When dried, thewhitish colored product has the attractive appearance of dried skimmilk.

If the product is at least partially gelled by control of operatingvariables in accordance with the teachings herein, only partial dryingor no drying at all need be practiced.

Although the inventive concepts will be readily understood from theforegoing description, by one having ordinary skill in this art, thefollowing illustrative examples are given to assure a completeunderstanding.

EXAMPLE 1 A. Soybeans are ground and the oil extracted with hexane togive flakes commonly called soybean meal. The flakes are added to anaqueous bath and a food grade alkaline reagent, sodium hydroxide, isadded until a pH of 10 is reached. The material is cooked for 30minutes, and then centrifuged. The soy protein material is precipitatedfrom the liquor by adding acetic acid until the isoelectric point isreached at about a pH of 4.7. The precipitate is washed with water, andthen added to water to make an aqueous slurry of 15 percent solids byweight.

B. The pH is then adjusted to 6.7 by adding sodium bicarbonate.

C. The slurry is then passed through a jet cooker under a pressure ofp.s.i.g., simultaneously with steam ejection from the jet cooker under apressure of p.s.i.g., into a pressure retention chamber at a pressure of75 p.s.i.g. The steam heats the slurry through the jet cooker to atemperature of 290 F. After 7 seconds, progressive portions of theheated slurry are suddenly discharged into a receiver at atmosphericpressure or below, causing flash off of vapors laden with obnoxioussmelling and tasting substances. The slurry is cooled by the flash offvaporization. The substance laden vapors are removed from the purifiedslurry.

D. The slurry is flash dried in a spray drier to a moisture content of 3percent.

,2. EXAMPLE 2 The steps A and B in Example 1 are followed, but in stepC,

. the slurry is heated to 260 F., held in the retention chamber for 15seconds, and ejected into a vacuum chamber at a pressure of p.s.i.

EXAMPLE 3 The step A in Example 1, followed by adjusting the pH in stepB to 5.7. In step C, the slurry, when passed through the jet cooker, isheated to a temperature of 340 F., retained for 30 seconds underpressure before discharging. When discharged and vapor flashed, theproduct is partially gelled.

EXAMPLE 4 Crushed full-fat soybeans, without hulls, are put into waterto make an aqueous slurry of a 20 percent solids content. The slurry ispassed through a jet cooker under a pressure of 75 p.s.i.g., with steam,and heated to 310 F. The slurry is held under a pressure of 70 p.s.i.g.for 50 seconds and then discharged to atmospheric pressure. Theresulting slurry is drum dried, and used as animal feed.

EXAMPLE 5 The steps A and B of Example 1 are performed except that thepH in step B is 7. 1. Then the slurry is passed through a high pressurepump and put under pressure of several hundred p.s.i., then passedthrough a hot zone flow tube and rapidly heated to a temperature of 250F., held under pressure for 12 seconds, and discharged to a vacuumchamber where the substance-laden vapors are removed. The product isthen freeze dried.

Hundreds of other examples could begiven but would only unduly lengthenthis description.

The functional characteristics of the novel product includes capacity toserve well as a water and fat binder in the slurry for homogenousdispersion thereof rather than separation. This facilitates its utilityin many products as a direct substitute for dairy products. It furtherhas excellent utility as a low calorie, high protein food. The proteincontent can be varied greatly depending upon whether other componentssuch as sugars, fiber etc., are initially removed, by adding controlledamounts of isolated soy protein (about 90 percent or greater protein) tothe slurry prior to the physical and thermal processing steps, or thelike.

Since the product can be used in a liquid slurry form with an edibleliquid carrier such as water which dissolves a share of the protein andholds the remainder in a finely divided suspension, it is useful forhigh protein beverages of various types, as liquid protein additives tofood products, or as a thickener. The product can also be used in powderor flake form as a cereal, as an additive to increase food proteincontent of such foods as spaghetti and macaroni, as a thickener forfoods, and as a protein supplement as for meat or imitation meats. Itcould be employed as the basic ingredient of puddings, as additives tobakery products such as cakes, cookies, and bread. Even when employed inproducts which are baked, broiled, fried, cooked, or otherwise heated,no objectionable odor arises with the presence of the soy product,thereby removing a substantial objection to its use by various segmentsof the food industry. The novel product in a powder form can beconverted to a paste which forms a high protein food spread of selectedflavors.

it also can be in the form of a semigelled or totally gelled productuseful in high protein, low calorie desserts, thickeners, candies, orimitation fruits of various types.

Additional food items formable by the product per se or as an additiveinclude coffee whiteners, spun protein fiber, in ice cream or assimulated ice cream, candy, pie crusts, crackers, chocolate, in butterand oleomargarine, snack dips, snack chips, sauces e.g., white, cheese,and hollandaise, as meat extenders as in sausage, in pie fillings, infrozen desserts, whip toppings, and marshmallows. Presentexperimentation is resulting in many other unique applications of thenovel vegetable protein, nondairy, negligible calorie, food products.The novel product can also be added to dairy products in various specialways to achieve totally new food products.

In view of the basic significance of this invention, and thebreakthrough it creates in vegetable protein food technology, it isconsidered that the invention is not to be specifically limited to thedisclosure details, but is to be defined by the scope of the appendedclaims and all reasonable equivalents.

I claim:

1. A process of continuously treating isolated soy protein comprisingthe steps of: forming a slurry of isolated soy protein having a pH ofabout 5.7 to about 7.5 and a solids content within the range of 5-17percent; practically instantly heating successive portions of the slurryto a temperature of about 220400 F., on a continuous basis whilephysically working it under dynamic flow conditions, subsequentlyretaining the slurry in the heated condition under positive pressure forat least a few seconds and up to a few minutes to cause changes in thesoy protein that improves the flavor thereof; and then suddenlyreleasing the pressure on successively advanced portions thereof, suchsudden pressure release causing flash off volatilization and removal ofwater vapor therefrom laden with noxious components that possessundesired flavor and odor characteristics, and separating the vaporsfrom the slurry to thereby result in a bland flavored soy proteinproduct.

2. The process in claim 1 wherein said temperature is about 285320 F.and said retaining step includes holding the slurry under pressure forabout 7 seconds to about seconds prior to pressure release.

3. A process of treating isolated soy protein to obtain a bland flavoredfood product comprising the steps of: preparing an aqueous slurry of theisolated soy protein having a pH of less than 8 and a solids contentwithin the range of 3-30 percent; heating the slurry rapidly anddynamically to elevated temperatures above about 220 F., and momentarilysubjecting it to dynamic physical working; retaining the slurry for abrief period of time under a positive pressure sufficiently high toprevent volatilization of heated water vapor from the heated slurry;suddenly releasing the pressure to cause flash off volatilization ofvapor laden with substances that possess undesired flavor and odorcharacteristics, and separating the vapors from the slurry to therebyleave a bland flavored isolated soy protein product.

4. The process according to claim 3 wherein said heating is to atemperature of about 220400 F. and is achieved by injecting steam intosaid slurry under pressure on a continuous flow basis, as said slurry isejected under pressure at a high velocity from a restricted passage.

5. The process according to claim 3 wherein said temperature is about285-320 F. and said retaining step includes holding the slurry underpressure for about 7 seconds to about 100 seconds prior to pressurerelease.

6. The process according to claim 3 wherein said aqueous slurry has asolids content of 5-17 percent by weight and wherein the bland flavoredisolated soy protein product is dried 7. The process according to claim3 wherein the temperature of the slurry is practically instantly heatedto a temperature of about 285-320 F. in a fraction of a second, and heldat that temperature for several seconds before pressure release, andthen is instantly lowered to below 212 F. with said pressure release.

8. The process according to claim 3 wherein the pH of the aqueous slurryis within the range of about 5.7 to about 7.5.

9. The process according to claim 8 wherein the slurry has a solidscontent of 5l7 percent and said heating is to a tem-. perature of about220-400 F. and is achieved by injecting steam into said slurry underpressure on a continuous flow basis as said slurry is ejected underpressure at a high velocity from a restricted passage.

on said heated slurry is released into a subatmospheric enclosure onwhich a negative pressure is drawn for optimum volatilization and forwithdrawing the volatilized water vapor with entrained noxiouscomponents.

14. The process according to claim 8 including the steps of flash-dryingthe slurry to form an isolated soy protein powder and forming a freshaqueous slurry from the powder prior to adjusting the pH of said freshaqueous slurry to a range between about 5.7 and 7.5.

2. The process in claim 1 wherein said temperature is about 285* - 320*F. and said retaining step includes holding the slurry under pressurefor about 7 seconds to about 100 seconds prior to pressure release.
 3. Aprocess of treating isolated soy protein to obtain a bland flavored foodproduct comprising the steps of: preparing an aqueous slurry of theisolated soy protein having a pH of less than 8 and a solids contentwithin the range of 3- 30 percent; heating the slurry rapidly anddynamically to elevated temperatures above about 220* F., andmomentarily subjecting it to dynamic physical working; retaining theslurry for a brief period of time under a positive pressure sufficientlyhigh to prevent volatilization of heated water vapor from the heatedslurry; suddenly releasing the pressure to cause flash offvolatilization of vapor laden with substances that possess undesiredflavor and odor characteristics, and separating the vapors from theslurry to thereby leave a bland flavored isolated soy protein product.4. The process according to claim 3 wherein said heating is to atemperature of about 220*-400* F. and is achieved by injecting steaminto said slurry under pressure on a continuous flow basis, as saidslurry is ejected under pressure at a high velocity from a restrictedpassage.
 5. The process according to claim 3 wherein said temperature isabout 285*-320* F. and said retaining step includes holding the slurryunder pressure for about 7 seconds to about 100 seconds prior topressure release.
 6. The process according to claim 3 wherein saidaqueous slurry has a solids content of 5- 17 percent by weight andwherein the bland flavored isolated soy protein product is dried
 7. Theprocess according to claim 3 wherein the temperature of the slurry ispractically instantly heated to a temperature of about 285* - 320* F. ina fraction of a second, and held at that temperature for several secondsbefore pressure release, and then is instantly lowered to below 212* F.with said pressure release.
 8. The process according to claim 3 whereinthe pH of the aqueous slurry is within The range of about 5.7 to about7.5.
 9. The process according to claim 8 wherein the slurry has a solidscontent of 5-- 17 percent and said heating is to a temperature of about220* - 400* F. and is achieved by injecting steam into said slurry underpressure on a continuous flow basis as said slurry is ejected underpressure at a high velocity from a restricted passage.
 10. The processaccording to claim 8 wherein said heating step includes heating theslurry to a temperature of about 220* -400* F. and said retaining stepincludes holding the slurry under pressure for about 7 seconds to about100 seconds prior to pressure release.
 11. The process according toclaim 10 wherein said temperature is about 285* - 320* F.
 12. Theprocess according to claim 8 wherein said pH range is 6.5 - 7.1.
 13. Theprocess according to claim 8 wherein the pressure on said heated slurryis released into a subatmospheric enclosure on which a negative pressureis drawn for optimum volatilization and for withdrawing the volatilizedwater vapor with entrained noxious components.
 14. The process accordingto claim 8 including the steps of flash-drying the slurry to form anisolated soy protein powder and forming a fresh aqueous slurry from thepowder prior to adjusting the pH of said fresh aqueous slurry to a rangebetween about 5.7 and 7.5.